diff --git a/lib/isc/include/isc/refcount.h b/lib/isc/include/isc/refcount.h
index 5d1a5d2bbf..1c9696fc6b 100644
--- a/lib/isc/include/isc/refcount.h
+++ b/lib/isc/include/isc/refcount.h
@@ -211,7 +211,7 @@ typedef struct isc_refcount {
 		ISC_ERROR_RUNTIMECHECK(_result == ISC_R_SUCCESS);	\
 	} while (0)
 
-#define isc_refcount_current(rp) ((unsigned int)((rp)->refs))
+unsigned int isc_refcount_current(isc_refcount_t *rp);
 
 /*%
  * Increments the reference count, returning the new value in
diff --git a/lib/isc/refcount.c b/lib/isc/refcount.c
index d83c82fe7f..0d961effe1 100644
--- a/lib/isc/refcount.c
+++ b/lib/isc/refcount.c
@@ -19,6 +19,21 @@
 #include <isc/result.h>
 #include <isc/util.h>
 
+#if defined(ISC_PLATFORM_USETHREADS) && !defined(ISC_REFCOUNT_HAVEATOMIC)
+unsigned int
+isc_refcount_current(isc_refcount_t *ref) {
+	isc_result_t result;
+	unsigned int answer;
+
+	result = isc_mutex_lock(&ref->lock);
+	ISC_ERROR_RUNTIMECHECK(result == ISC_R_SUCCESS);
+	answer = ref->refs;
+	result = isc_mutex_unlock(&ref->lock);
+	ISC_ERROR_RUNTIMECHECK(result == ISC_R_SUCCESS);
+	return (answer);
+}
+#endif
+
 isc_result_t
 isc_refcount_init(isc_refcount_t *ref, unsigned int n) {
 	REQUIRE(ref != NULL);